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Improved Polycrystalline YBa2Cu3O7- Superconductor Material

IP.com Disclosure Number: IPCOM000108726D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Chance, D: AUTHOR [+3]

Abstract

The superconducting properties of high temperature superconductors in dense polycrystalline form are determined by the properties of the grains and the grain boundaries. Typically, the sintered material has grains up to hundreds of microns in size, and the thermal expansion anisotropy of YBa2Cu3O7-w causes extensive cracking during cooling. Such cracking reduces the critical current densities in the superconducting state by orders of magnitude. Cracking has been shown to be eliminated by reducing the grain size to about one micron (1). The conventional methods used to produce small grain size in the sintered specimen require either a very small starting grain size and/or low sintering temperatures to avoid grain growth. We disclose a method of preparing fine grained YBa2Cu3O7-w doped with up to 1 atomic % Ag.

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Improved Polycrystalline YBa2Cu3O7-  Superconductor Material

       The superconducting properties of high temperature
superconductors in dense polycrystalline form are determined by the
properties of the grains and the grain boundaries. Typically, the
sintered material has grains up to hundreds of microns in size, and
the thermal expansion anisotropy of YBa2Cu3O7-w causes extensive
cracking during cooling.  Such cracking reduces the critical current
densities in the superconducting state by orders of magnitude.
Cracking has been shown to be eliminated by reducing the grain size
to about one micron (1).  The conventional methods used to produce
small grain size in the sintered specimen require either a very small
starting grain size and/or low sintering temperatures to avoid grain
growth.  We disclose a method of preparing fine grained YBa2Cu3O7-w
doped with up to 1 atomic % Ag.  The Ag substitutes for Cu in the
YBa2Cu3O7-w crystal structure with some enrichment at the grain
boundaries. This produces a fine grained microstructure with better
superconducting coupling across the grains (2).

      The experimental procedure involves the following steps:  The
oxides or nitrates of Y, Ba, Cu and Ag are mixed in required atomic
ratios and dissolved in HNO3.  The solution is diluted to prevent
precipitation of any nitrates.  This solution is then spray-dried to
produce fine and very homogeneous mixture of the nitrates.  The
powder is then heated in pure oxygen a...